[Feature Request]: Support substitutions in inline code

[eedugon]

Prerequisites

• I have searched existing issues to ensure this feature hasn't already been requested
• I have tested using the latest version of docs-builder

What problem are you trying to solve?

At the moment we don't support substitutions in inline code blocks, like:

`{{my-sub}}`.

In some cases we generate sections of the pages from snippets that receive certain substitutions, and we should be able to play with the format of those substitutions.

There's an example of this need in this PR: elastic/docs-content#1457

Proposed Solution

Implement something similar as with the normal code blocks that support the subs=true option.

Examples and Research

No response

Alternative Solutions

No response

Additional Context

No response

How important is this feature to you?

Nice to have